Instrument control linkage

ABSTRACT

A control linkage for a recording type instrument which connects a sensing element to an indicating element. The control linkage is comprised of an element input link which moves a follower. The follower is captured to a guide means associated with a laterally arranged rail. A second follower is captured within the guide means of a second rail, with the two followers being connected together by an interconnecting link. An output link connected to the second follower actuates the indicating element. A sensor element pivotally moves the element input link which in turn causes pivotal movement of the output link by means of the control linkage. The accuracy attained with the control linkage is much greater than that of the prior art bell crank system.

[ INSTRUMENT CONTROL LINKAGE [76] Inventor: Nolan Smiley, Jr., P. O. Box916,

McCamey, Tex. 79752 22 Filed: Feb. 8, 1972 [21] Appl.No.: 224,461

[52] US. Cl. 74/96 [51] Int. Cl. Fl6h 21/44 [58] Field of Search 74/96,98, 99, 29; 73/411, 412

[56] References Cited UNlTED STATES PATENTS 1,923,240 8/1933 Tarr 73/4111,993,637 3/1935 Wardenburg.. 73/411 2,644,335 7/1953 Dickie 73/4113,075,390 1/1963 Sheppard... 73/411 2,859,554 11/1958 Walss 74/993,062,062 1l/1962 Loomis 74/99 3,092,344 6/1963 Dinsmore et al. 74/993,475,973 ll/l969 Blazek et al. 74/29 Primary Examiner-Charles J. MyhreAssistant Examiner-Wesley S. Ratliff, Jr. Att0rney-Marcus L. Bates [5 7]ABSTRACT A control linkage for a recording type instrument whichconnects a sensing element to an indicating element. The control linkageis comprised of an element input link which moves a follower. Thefollower is captured to a guide means associated with a laterallyarranged rail. A second follower is captured within the guide means of asecond rail, with the two followers being connected together by aninterconnecting link. An output link connected to the second followeractuates the indicating element.

A sensor element pivotally moves the element input link which in turncauses pivotal movement of the output link by means of the controllinkage. The accuracy attained with the control linkage is much greaterthan that of the prior art bell crank system.

8 Claims, 7 Drawing Figures INSTRUMENT CONTROL LINKAGE BACKGROUND OF THEINVENTION Recorder type instruments having a pointer which is suppliedwith a pin or stylus arranged to print out on a moving paper chart areold in the art. Some recorders use a circular chart, while others use aroll chart which is continuously unwound from a roll or a drum. Thespeed of the chart is usually governed by a clock in order to providefor a plot-against time.

In the prior art recorders, such as for example recorder Model 40manufactured by the Foxboro Company, or recorder series FS and SSmanufactured by the American Meter Company, the control linkage whichinterconnects the sensor element to the stylus is usually comprised ofbell-cranks connected together by a crossover link. The non-linearity ofthe control linkage inherently produces an error in recording onto thechart the signal received from the sensor element.

The sensing element, which can be a pressure element such as a bourdontube, usually leaves the manufacturer in a condition whereby themagnitude of the signal relative to the movement of the element inputlink is linear. However, as the sensor element becomes old it must bereplaced because its characteristics change, although its linearity isstill present. That is, change in the characteristics of the elementoccurs, although the element remains linear over a limited range ofpressure.

It is therefore desirable to provide improvements in a control linkagefor connecting a sensor element to an indicating element wherein thecontrol linkage is inherently more accurate than similar prior artdevices, and wherein the control linkage can be used in conjunction withsensor elements which have changed characteristics, but have not losttheir linearity.

SUMMARY OF THE INVENTION In an instrument having a sensing elementconnected to an indicating element, a control linkage for connecting thesensor element to the indicating element, comprising: an element inputlink connected to a primary follower. The primary follower is capturedto a laterally arranged rail, wherein the follower can travellongitudinally of the rail and of the input link. A secondary followeris captured by a longitudinally extending marginal end portion of anoutput link and also by a longitudinally disposed guide means formed ona second rail. The two followers are connected together by aninterconnecting link so that the sensor element moves the element inputlink which in turn moves the output link by means of the improvedcontrol linkage.

The unexpected advantage in the improvements of this invention includesincreased accuracy in measuring when the improved control linkage issubstituted for some prior art control linkages, and in utilizing theimproved control linkage in conjunction with sensor elements which havechanged characteristics.

A primary object of this invention is the provision of improvements incontrol linkages.

Another object of the invention is to provide a control linkage forconnecting a sensor element to an indicating element wherein theindicating element more accurately reproduces the signal or the movementof the sensor element.

A further object of this invention is to disclose and provide a controllinkage which can be directly substituted for prior art controllinkages, so that replacement of the sensor element is often avoided,and at the same time the accuracy of measurement is increased.

A still further object of this invention is to provide a control linkagefor connecting a sensor element to an indicating element whicheliminates some of the criticality heretofore associated with a sensorelement.

Another object of this invention is to provide a control linkage whichincreases the linearity involved in measuring signal magnitude.

An additional object is to provide a control linkage for connecting asensor element to an indicating element of a recording instrument whichis rugged in construction, inexpensive to manufacture, less complicatedin design, and which is accurate over its entire range as compared tosimilar prior art devices.

These and various other objects and advantages of the invention wilbecome readily apparent to those skilled in the art upon reading thefollowing detailed description and claims and by referring to theaccompanying drawings.

The above objects are attained in accordance with the present inventionby the provision of a combination of elements which are fabricated in amanner substantially as described in the above abstract and summary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a part diagrammatical, partschematical, fragmentary representation of a prior art control linkage,with parts thereof being broken away so as to conserve drawing space;

FIG. 2 is a diagrammatical, fragmentary representation of a controllinkage made in accordance with the present invention;

FIG. 3 is an elarged fragmentary enlarged which sets forth onemodification of part of the apparatus disclosed in FIG. 2;

FIG. 4 is an enlarged, fragmentary, part-crosssectional exploded viewtaken along line 4 -4 of FIG.

FIG. 5 is a schematical representation of another form of the invention;

FIG. 6 is an enlarged, fragmentary,cross-sectional representation as maybe taken along line 66 of FIG. 5, for example, and

FIG. 7 is a broken perspective view of the present invention,illustrated in its operative configuration in conjunction with someprior art apparatus.

DETAILED DESCRIPTION OF THE DRAWINGS Throughout the various figures ofthe drawings, like numerals will occasionally be used to indicate likeelements whenever it appears logical to do so.

In FIG. 1, a simplified prior art representation of part of aninstrument is shown, wherein a sensor element 10 is affixed by means ofelement 11 to any convenient portion of the housing or base of aninstrument, in the usual manner. An element input link 12 is providedwith the usual element input pivot 13 so that the sensor element canpivotally move the depending end 14 of the link about the pivot. End 14is journaled to a crossover link 15, hereinafter called aninterconnecting link. The depending end of the interconnecting link isjournaled at 16 to the depending end of an output link 17. The outputlink is pivotally affixed to the main body of an instrument by means ofan output pivot 18. Pin 21 is affixed to and moves with link 17, and isprovided with the illustrated stylus thereon. Portion 17, is acontinuation of link 17 and is journaled at 19 to member 20 so thatvarious functions or modifications of the signal characteristics can beimparted into the apparatus, as is known to those skilled in the art.

Looking now to the details of the remaining figures, which disclose theinvention, and wherein a control linkage made in accordance with thepresent invention is illustrated. There is seen diagrammaticallyillustrated in FIG. 2 a pivoted end of an element input link, themarginal end of which has been provided with a guide means 24 in theform of a longitudinally extending slot.

A rail 25 is provided with a fastener means at pivoted end 26, and aguide means 27 disposed longitudinally of the rail. The guide means isin the form of a slot.

A primary follower 28 is captured within each of the guide means and ismovable therewithin in accordance with the relative position of theelement input link and the rail.

An interconnecting link 29 having adjustment 29' interposed therein hasone depending end thereof connected to the primary follower. The outputlink has a terminal end 30 inwardly of which there is disposed alongitudinally extending guide means 31 in the form of a slot. Guidemeans 32 is in the form of a slot which is longitudinally disposed alonga secondary rail 33. Fastener 34 forms a pivot point about which therail can be pivoted any desired amount allowed by the circumferentiallyextending length of groove 132 formed within mount 133. The mount isaffixed to structure associated with the instrument housing (not shown).The before mentioned fastener means 26 cooperates in a similar mannerwith the groove 132' formed within the mount means 133'.

A secondary follower 35 is attached to the remaining depending end ofthe interconnecting link. The follower is captured within the two guidemeans provided by the secondary rail and the output link. Hence, it isevident that if desired, the two followers, the two spaced apart rails,and the guide means may be identical in construction. The primary railassociated with the drive element preferably is arranged relative to theinput link and interconnecting link, as illustrated at 25.

FIGS. 3 and 4 set forth in greater detail a modification of FIG. 2wherein apparatus 41 can be utilized as either the primary or secondaryportion of the control linkage assembly disclosed in FIG. 2. Theapparatus includes a body 42 having a bifurcated depending end 43 whichis provided with the illustrated diametrically arranged fastener means44. The opposed end 45 has a guide means 46 formed therein, which forpurposes of illustration is shown as being in the form of an elongatedlongitudinally disposed slot. Follower 47 pivotally captures a terminalend portion of interconnecting linkage 48 in aligned relationship withthe guide means. The linkage 48 is disposed 45 relative to the rail andaccordingly body 42 is equivalent to input link 12.

Rail 49 is provided with guide means 50 which, for the purpose ofillustration is shown to be in the form of a longitudinally extendinggroove. Spring 51 vertically depends in a downward direction and is bentrearwardly into underlying relationship relative to the rail so that thevarious illustrated parts are maintained properly assembled in capturedrelationship relative to one another. Split washer 52 is received withinthe illustrated groove 53 of the follower, while split washer 54 isreceived within groove 55 with the main body 42 being sandwichedtherebetween in the indicated manner of FIGS. 3 and 4. Conical portion56 of the follower is slidably received within groove 50 and can bemoved from one extremity of the groove to the other by the input link.

Looking now to the details of FIGS. 5 and 6 which set forth stillanother form of the invention disclosed in the previous figures, andwherein interconnecting link 29 is seen to be affixed to the rail andthe link by a fastener means 28. The fastener means is provided with alow friction roller 63 which is slidably received upon the shank portionof the fastener, with a washer 62 preventing end 61 of the fastener frombecoming disengaged therefrom.

A more detailed operative form of one of the embodiments of theinvention is disclosed in FIG. 7, wherein the control linkage 65interconnects a sensor element to an indicating element. As seenillustrated in the figure, an output link 66 is connected to portion 67by means of micrometer adjustment 68. Enlarged end portion 69 of thelink is removably affixed to the depending free end of shaft 71. Theshaft is joumaled to plate member 70 which in turn is affixed to orforms part of the instrument housing. Stop means 72 limits the travel ofthe output linkage as it is pivoted by the shaft. Adjustment 73 is adamper with which those skilled in the art are familiar. Link 74, whichcan be considered to be a continuation of 67, is provided with guidemeans 75. Rail 76 includes a guide means 77 longitudinally disposedtherein.

lnterconnecting link 78 is affixed to follower 80 as in the beforedescribed manner of FIGS. 2-6 while the remaining opposed end portion 81is affixed to the primary follower 82. Rail 83 is provided with theillustrated guide means which is arranged 45 relative to theinterconnecting link. The output linkage 84 includes the illustratedguide means formed therein. Input shaft 85 is anchored to the inlargedend portion of input link 84 and moves the follower 82 in response tomovement thereof.

Adjustment 86 provides for large changes in the length of theinterconnecting link, while micrometer adjustment 87 provides for smalladjustments. I-Iub 88 supports shaft housing 89 and is affixed to thebase of the instrument. A sensing element is naturally affixed to anddrives the shaft 85.

In operation, the apparatus disclosed in FIGS. 3 and 4 can besubstituted for the control linkage of a prior art recording instrumentin the illustrated manner of FIG. 7, for example.

The operation of the apparatus is best understood by comparing theembodiment of FIG. 2 with the prior art apparatus of FIG. 1. In FIG. 1,the bourdon tube 10 is connected to a flow conduit and receives apressure signal which causes the input link 12 to pivotally move aboutpivot 13, thereby moving pin 21 an amount which is dependent upon themechanical advantage presented by the differences in the length of theinput and output links 12 and 17, respectively. The minimum error of therecorded signal placed upon chart 22 occurs when the input and outputlinks are arranged perpendicularly with respect to the cross-over link.

In order to still further reduce this inherent error which occurs inmeasuring the signal received at 10, the element input and output linksare modified in accordance with FIGS. 2 and 7 by incorporating thereonapparatus made in accordance with the teachings of FIGS. 3-6. As seen inthe schematical representation of FIG. 2, as the input link pivots aboutthe input pivot, the follower is forced to move within the guide means27. While the guide means is illustrated as being arranged laterallywith respect to the input link, it should be understood that it ispreferred that the guide means be arranged along line and notnecessarily disposed perpendicularly to the input link, as evidenced bythe adjustment means 133' and 26. Since the pivoted end 23 of the inputlink moves both longitudinally and arcuately relative to the rail, thefollower moves longitudinally of the guide means 24 and 27, with theguide means moving the interconnecting link an amount which is directlyproportional to the movement effected by the sensor element.

The secondary follower is captured within the guide means of thesecondary rail and the output link, and as the output link is moved bythe interconnecting link, the follower is free to move longitudinallywithin each of the guide means, thereby moving the secondary follower anamount directly proportional to the movement of the primary follower 28.The multiplication of a pen connected to link 17' is dependent upon therelative lengths of the input and output links, as well as the relativeposition of slots 27 and 32.

In the specific illustration of FIG. 7, the present invention has beenadapted for use in an American Series FS or SS dry flow orifice metermanufactured by the American Meter- Company.

As seen in the illustration of FIG. 7, elements 74, 76; and element 83,84 are essentially the apparatus disclosed in FIGS. 3 and 4. As thesensing element rotates shaft 85, lever 84, which is the input link,moves follower 82 within the guide means, so that interconnecting link78 moves follower 80. The follower 80 likewise is disposed within itsassociated guide means and moves output linkage 74 in response tomovement of shaft 85. The output link moves shaft 71 which in turn movesthe pin 66, thereby enabling a stylus or the like to draw a curve on amoving graph which is indicative of and proportional to movement ofshaft 85.

In order to calibrate the apparatus of FIG. 7, the reference pressure onthe primary element should provide a 0 on the chart, ie, if 3 psi is 0and 15 psi is 100% range, then 3 psi imposed upon the element shouldcause pin 66 to assume a position which causes the stylus to draw acurve at the 0 reading on the chart. Should an adjustment be required,the rail 83 is moved about its pivoted end until the 0 reading-isattained. If the interconnecting linkage 78 has been properly adjustedat 86 and 87, then the and reference pressure on the primary elementwill now provide for its proper proportion of the 100% of range.

The present invention enables the primary element tobe made smaller andmore rugged with less movement being effected, as compared to thepriorart linkage. Where a bellows is used, less convolutions can beutilized therein, thereby providing for a more inexpensive and a morerugged bellows.

' Often a primary sensor, such as a bourdon tube, must be renewed andthe old one discarded, because its deflection characteristics havechanged, although it still remains linear. This is usually due to thebourdon tube having been overstressed or having been used in highpressure applications over an extended period of time.

With the present invention it is unnecessary to change the expensivebourdon tube merely because the deflection characteristics have changed,because the present invention enables the rails thereof to be adjustedso as to attain a proper reading on the chart which is consistent withthe range of the reference pressure.

The accuracy of the present invention depends upon the drive angle, asin the prior art systems; however, for any particular angle ofdisplacement the present invention is approximately twice as accurate asthe prior art system of FIG. 1. Where the prior art system approaches 1percent accuracy, the present invention approaches /6 percent accuracy,for example. The present invention can be rapidly adjusted, and can bedirectly substituted for the control linkage of many prior art systems,and the accuracy attainable is believed to be duplicated only byelectronic measuring devices.

It should be understood that it is unnecessary to render both theprimary and secondary rails adjustable, and that where desirable, theassembly disclosed in FIGS. 3-5 can be used in conjunction withapparatus other than recorders.

I claim:

1. In combination with a recording type instrument having a sensingelement and an indicating element, a control linkage connecting thesensor element to the indicating element comprising:

an input link having guide means formed thereon;

means pivotally mounting said input link to cause said guide meansthereof to be pivotally moved in response to movement of the sensorelement; a rail having guide means formed thereon; and aninterconnecting link having a follower formed thereon; means by whichsaid follower is captured by each said guide means so that said followercan be moved longitudinally along each said guide means; a second rail,guide means formed on said second rail, an output link, guide meansformed on said output link, a second follower affixed to saidinterconnecting link;

means by which said second follower is captured by and moveslongitudinally along said guide means of said second rail and saidoutput link;

means pivotally mounting 'said output link to cause said guide meansthereof to be pivotally moved by said second follower; means connectingsaid output link to said indicating element so that movement of saidinput link by said sensor causes a proportional movement of saidindicating element.

2. The control linkage of claim 1 wherein said guide means formed onsaid input link is a longitudinally extending slot formed in a marginalend portion thereof; said guide means formed on the first recited railbeing a longitudinally extending slot formed in a marginal portion ofsaid first rail;

means mounting said first rail with the slot thereof being superimposedupon the slot of said input link; the first said follower being receivedwithin the said slot of the first rail and the slot of the input link sothat pivotal movement of said input link causes the first said followerto move longitudinally within each of the slots to which it isconnected, thereby causing said interconnecting link to be moved inresponse to movement of said input link.

3. The control linkage of claim 1 wherein said guide means formed onsaid output link is a longitudinally extending slot formed in a marginalend portion thereof;

said guide means formed on said second rail is a longitudinallyextending slot formed in a marginal portion thereof;

means mounting said second rail with the slot thereof being superimposedupon and arranged at an intersecting angle with respect to the slot ofsaid output link; each said follower extending through each said slot sothat pivotal movement of said output link causes each said follower tomove longitudinally within each said slot, and to cause saidinterconnecting link to be moved in response to movement of said inputlink. 4. In an instrument having a sensor and an indicator, a controllinkage for connecting the sensor to move the indicator comprising abase, an input link, and an output link; means by which said input andoutput links are pivotally affixed to said base;

guide means formed longitudinally along a marginal pivoted end of saidinput link, guide means formed longitudinally along a marginal pivotedend of said output link; spaced rails, means supporting said rails fromthe base so that the relationship of the rails can be changed relativeto one another; guide means formed in each said rail; said guide meansof said input link being superimposed upon and arranged at anintersecting angle respective of the guide means of one said rail; saidguide means of said output link being superimposed upon and arranged atan intersecting angle respective of the guide means of the remainingsaid rail; an interconnecting link having a follower means formed at thedepending ends thereof; one said follower means being captured withinsaid superimposed guide means of said input link and rail; the remainingfollower means being captured within said superimposed guide means ofsaid output link and rail;

whereby: movement of said input link moves the follower within the guidemeans of said input link and its rail to thereby move saidinterconnecting link, which imparts movement into the second follower,which imparts movement into said output link.

5. The control linkage of claim 4 wherein said guide means is elongatedand longitudinally extending in form and which receives said followerthereon so that said follower can move longitudinally of the guide fromone to the other limits thereof.

6. The control linkage of claim 4 wherein said guide means formed onsaid input link is a longitudinally extending slot formed in a marginalend portion thereof; said guide means formed on said rail is alongitudinally extending slot formed in a marginal portion of said rail;

means mounting said rail with the slot thereof being superimposed uponand arranged to form an intersecting angle with respect to the slot ofsaid input link;

said follower extending through each of said superimposed slots so thatpivotal movement of said input link causes said follower to movelongitudinally within each said slot, and to casue said interconnectinglink to be moved in response to movement of said input link.

7. The control linkage of claim 4 wherein said guide means in one saidrail is a longitudinally extending groove, and said guide means in saidinput link is a longitudinally extending slot; said follower extendingthrough the last said slot and into registry with said groove.

8. The control linkage of claim 4 wherein each said rail includes meansby which the guide means thereof can be pivotally moved so as to changethe relative position of the guide means respective to theinterconnecting link.

1. In combination with a recording type instrument having a sensingelement and an indicating element, a control linkage connecting thesensor element to the indicating element comprising: an input linkhaving guide means formed thereon; means pivotally mounting said inputlink to cause said guide means thereof to be pivotally moved in responseto movement of the sensor element; a rail having guide means formedthereon; and an interconnecting link having a follower formed thereon;means by which said follower is captured by each said guide means sothat said follower can be moved longitudinally along each said guidemeans; a second rail, guide means formed on said second rail, an outputlink, guide means formed on said output link, a second follower affixedto said interconnecting link; means by which said second follower iscaptured by and moves longitudinally along said guide means of saidsecond rail and said output link; means pivotally mounting said outputlink to cause said guide means thereof to be pivotally moved by saidsecond follower; means connecting said output link to said indicatingelement so that movement of said input link by said sensor causes aproportional movement of said indicating element.
 2. The control linkageof claim 1 wherein said guide means formed on said input link is alongitudinally extending slot formed in a marginal end portion thereof;said guide means formed on the first recited rail being a longitudinallyextending slot formed in a marginal portion of said first rail; meansmounting said first rail with the slot thereof being superimposed uponthe slot of said input link; the first said follower being receivedwithin the said slot of the first rail and the slot of the input link sothat pivotal movement of said input link causes the first said followerto move longitudinally within each of the slots to which it isconnected, thereby causing said interconnecting link to be moved inresponse to movement of said input link.
 3. The control linkage of claim1 wherein said guide means formed on said output link is alongitudinally extending slot formed in a marginal end portion thereof;said guide means formed on said second rail is a longitudinallyextending slot formed in a marginal portion thereof; means mounting saidsecond rail with the slot thereof being superimposed upon and arrangedat an intersecting angle with respect to the slot of said output link;each said follower extending through each said slot so that pivotalmovement of said output link causes each said follower to movelongitudinally within each said slot, and to cause said interconnectinglink to be moved in response to movement of said input link.
 4. In aninstrument having a sensor and an indicator, a control linkage forconnecting the sensor to move the indicator comprising a base, an inputlink, and an output link; means by which said input and output links arepivotally affixed to said base; guide means formed longitudinally alonga marginal pivoted end of said input link, guide means formedlongitudinally along a marginal pivoted end of said output link; spacedrails, means supporting said rails from the base so that therelationship of the rails can be changed relative to one another; guidemeans formed in each said rail; said guide means of said input linkbeing superimposed upon and arranged at an intersecting angle respectiveof the guide means of one said rail; said guide means of said outputlink being superimposed upon and arranged at an intersecting anglerespective of the guide means of the remaining said rail; aninterconnecting link having a follower means formed at the dependingends thereof; one said follower means being captured within saidsuperimposed guide means of said input link and rail; the remainingfollower means being captured within said superimposed guide means ofsaid output link and rail; whereby: movement of said input link movesthe follower within the guide means of said input link and its rail tothereby move said interconnecting link, which imparts movement into thesecond follower, which imparts movement into said output link.
 5. Thecontrol linkage of claim 4 wherein said guide means is elongated andlongitudinally extendIng in form and which receives said followerthereon so that said follower can move longitudinally of the guide fromone to the other limits thereof.
 6. The control linkage of claim 4wherein said guide means formed on said input link is a longitudinallyextending slot formed in a marginal end portion thereof; said guidemeans formed on said rail is a longitudinally extending slot formed in amarginal portion of said rail; means mounting said rail with the slotthereof being superimposed upon and arranged to form an intersectingangle with respect to the slot of said input link; said followerextending through each of said super-imposed slots so that pivotalmovement of said input link causes said follower to move longitudinallywithin each said slot, and to cause said interconnecting link to bemoved in response to movement of said input link.
 7. The control linkageof claim 4 wherein said guide means in one said rail is a longitudinallyextending groove, and said guide means in said input link is alongitudinally extending slot; said follower extending through the lastsaid slot and into registry with said groove.
 8. The control linkage ofclaim 4 wherein each said rail includes means by which the guide meansthereof can be pivotally moved so as to change the relative position ofthe guide means respective to the interconnecting link.